This invention relates generally to a circuit arrangement for controlling the operation of a sewing machine, and particularly the present invention relates to needle positioning in a sewing machine.
The needle of a sewing machine is arranged to be driven by an electrical motor to be periodically moved up and down, and is further arranged to be stopped at a predetetmined position when a foot pedal used for controlling the driving speed of the needle is put in neutral position. In order to effect such needle positioning control conventional sewing machine controlling circuitry is arranged to control the operating speed of the sewing machine with the speed being sufficiently reduced as is disclosed in Japanese Patent Provisional Publication No. 54-150243. However, when effecting such needle positioning control, the driving speed of the needle is set to a very low value so as to accurately position the needle at a predetermined resting position in which the needle is penetrating a piece of cloth to be sewed or is spaced apart from the cloth. Due to such a low moving speed of the needle, it takes a relatively long time period for a last stitch just before the needle is positioned at the predetermined resting position. Such a long time results in low efficiency of sewing operation. However, needle moving speed during positioning control cannot be simply set to a high value because high speed positioning control results in inaccurate positioning.